The present invention relates to a semiconductor processing apparatus, and more particularly, to a semiconductor processing apparatus which predicts processing results to improve the operating rate and reliability of the apparatus and a method of monitoring and/or controlling the semiconductor processing apparatus.
In recent years, the dimensions of semiconductor devices have been miniaturized more and more, so that a severe manufacturing dimension accuracy is required to such an extent that a gate electrode of 0.1 μm or smaller should be processed in a dimensional accuracy of 10% or less. On the other hand, in a semiconductor manufacturing apparatus for processing a semiconductor wafer using heat and plasma and reaction products, resulting from chemical reactions within the apparatus, are attached and remain on inner walls of the apparatus. Such reaction products change a wafer processing state in the apparatus over time. For this reason, as a number of wafers are sequentially processed by the semiconductor manufacturing apparatus, the shape of semiconductor devices on wafers gradually changes to cause deteriorated performance. To accommodate this problem, generally, various countermeasures have been taken. For example, the inner walls of the chamber are cleaned using plasma to remove products attached thereon, or the walls of the chamber are heated so that products are less likely to adhere on the inner walls. However, in most cases, such countermeasures are not perfect, inevitably resulting in a gradual change in the shape of processed semiconductor devices. For this reason, the manufacturing apparatus must undergo replacement of parts and wet cleaning before the shape of processed devices changes so as to cause a problem. In addition, fluctuations in a variety of states of the apparatus involve in variations in the shape of devices processed on wafers, other than deposited films. To address these problems, there have been created techniques for detecting a change in a processing state within a semiconductor manufacturing apparatus and feeding back the result of detection to the input of the semiconductor manufacturing apparatus to maintain the processing state constant.
Such a method of monitoring fluctuations in plasma processing is disclosed, for example, in JP-A-10-125660. This official document shows a method of predicting the performance of an apparatus and diagnosing the state of plasma using an equation representing the relationship between plasma processing characteristics and electric signals generated in the apparatus. Specifically, JP-A-10-125660 discloses a method of deriving an approximate expression which represents the relationship between three electric signals and the plasma processing characteristics of the apparatus through multiple regression. Another example is disclosed in JP-A-11-87323. A method disclosed in JP-A-11-87323 adapts a general detection system having a multiplicity of existing detectors mounted thereon to a semiconductor manufacturing apparatus to monitor the state of the apparatus from a correlation signal of signals detected by the detectors. Specifically, the correlation signal is generated by a calculation based on the ratio of six electric signals. A further example is disclosed in U.S. Pat. No. 5,658,423. This U.S. patent discloses a method of monitoring the state of an apparatus by capturing a number of signals from a light and a mass analyzer to generate a correlation signal for monitoring. The correlation signal is generated using a principal component analysis.